1. Technical Field
The present invention relates to a signal transmission device for performing data transmission.
2. Background Art
Recently, a technique in which data transmission between a variety of electronic devices mounted on a vehicle, such as an automobile, is performed by an optical cable is known. The electronic devices connected by the optical cable have connectors for connecting the optical cable, and the connector has a photoelectric conversion module referred to as FOT (Fiber Optic Transceiver). The photoelectric conversion module performs conversion between an optical signal and an electric signal.
For example, the photoelectric conversion module having a transmission function essentially consists of a light-emitting element and an element driving IC. In this case, the element driving IC functions as a signal transmission device for performing data transmission, and outputs an optical signal depending on an electric signal, which is a data signal from a control circuit of the electronic devices, by driving the light-emitting element.
In this photoelectric conversion module, because the output power and the extinction ratio of the light-emitting element are varied depending on a temperature, it is necessary to control a current value depending on the temperature by the element driving IC to keep constantly the output power and the extinction ratio (i.e., temperature compensation). For example, a light-emitting device having a function of temperature compensation of a light-emitting element is disclosed in JP-A-2007-324493. For the light-emitting device, a temperature signal detected by a temperature compensation circuit is inputted to an input terminal of a power supply circuit. Accordingly, the power supply circuit is configured to decrease an output voltage thereof depending on a temperature signal indicating that an increase of an ambient temperature is detected, and contrarily, to increase the output voltage depending on a temperature signal indicating that a decrease of the ambient temperature is detected.